Local services are typically provided in today's telecommunications network by a class 5 switching system. The class 5 switch is a monolithic system generally containing a central computing unit, matrix, line modules, trunk modules, and service circuits. These components are typically tightly coupled forming a proprietary control architecture controlled by the central computing unit.
The digital loop carrier is being widely deployed to connect business and residential telephone customers to the class 5 central office switch. However, today's the central office switching systems were not initially designed with digital loop carriers or fiber optic loop equipment in mind. Nor were they designed for long holding times, extensive intelligent network signaling loads, or multimedia control. In particular, long call hold times related to the rapid rise in the volume of data calls, have resulted in increased service blockages in the end office switches.
Further, class 5 switching systems generally contain a number of standard local services or features such as Class, Centrex, and Operator Services. Because of its monolithic and tightly coupled architecture, the class 5 switching system is usually comprised of components supplied by a single equipment manufacturer. Thus, when new services or features are desired, a network operator must request their implementation from the class 5 switch manufacturer. Due to the monolithic nature of the class 5 switching system, service and feature implementation are generally tightly coupled to the architecture of the switch. Therefore, new services and features are usually very costly to implement and require significant time to market. These costs and lead times for software upgrades led to the industry architecture known as Advanced Intelligent Network in the late 1980s as a way for Local Exchange Carriers (LECs) to gain control of software development for new features. This process itself has been largely ineffective due to slow deployment and high costs.